Onions are the basis of so many recipes that it’s hardly surprising to learn that they are one of the oldest cultivated vegetables. With such a long history, you’d expect there to be huge diversity of varieties available but most supermarkets only ever seem to stock the standard round brown ones. So how does the enthusiast get hold of a flat white, long red or a mini cocktail?

The usual answer is to grow them yourself, but the most common way of growing onions is from ‘sets’, which are really just mini onions that are planted either in autumn or spring. Here the same problem arises, in that those sold for planting are much the same as their supermarket counterparts. The true onion connoisseur has to get their head around growing from seed to access the fantastic range of varieties out there, but this needn’t be daunting as long as you have a glasshouse or sunny windowsill to start the seeds off.

Sow easy

Onions in the Kitchen Garden at Hampton Court Palace in 2014.

Some books will tell you to sow on Boxing Day, but I suspect that’s just an excuse to get out of the washing up. In practice, any time in January and February is good. At Hampton Court Palace Kitchen Garden, we sow our onion seeds into trays of modules, planting about five seeds in each module. They will spend more time than most seedlings in their seed trays, so either use a richer compost mix, such as John Innes No. 2, or some supplementary feeding with an organic, nitrogen rich fertiliser may be necessary.

In early April each module with the five seedlings get planted out in rows about 20 cm apart with 30 cm between rows. They will grow as a clump, a bit like shallots, but still giving good sized onions come harvest time. It’s a great technique as you can fit a lot more than you’d think into a small area using this method.

Onions to try

My favourite varieties are ‘Rossa di Firenze’ (aka ‘Long Red Florence’), which is an Italian heirloom variety, with mild, red, torpedo shaped bulbs which can get quite large. ‘Early Paris White’ is almost disc shaped and will give an early crop, it’s best harvested whilst the leaves are still green. ‘White Sweet Spanish’ and ‘Walla Walla Sweet’ are mild enough to eat raw; for the sweetest bulbs give them some shade and plenty of water and enjoy in salads. Conversely, if you like your onions to pack a punch, grow standard varieties in full sunshine and spare the water, as this will stress the plants and make them more pungent.

Perennial onions

If you don’t have much space, consider growing some of the perennial, clump forming types. These will quietly multiply in a corner of the garden and you can pull off a few stems at a time to use like spring onions. Welsch onions can be treated like this (and before you ask, that’s not a typo, the Welsch bit is from the old German word for foreign), but my favourite, if you can find a source for them, is the true Pearl Onion. This is actually a type of leek (Allium ampeloprasum) but tastes like a garlicky spring onion. The bulbs quickly multiply in the years after planting to form dense clumps that start growing in September and then stay green through till May, giving you a tasty supply of ‘spring’ onions. By June they have sent up pretty purple pompom flower-heads, and when all the leaves and flowers die back you can dig up the clump to find lots of white cocktail onions, up to an inch across. Take the biggest to eat in stews or pickled and replant the rest to repeat the process next year. Given their versatility I can’t believe they’re not more widely available, but the Heritage Seed Library has a variety called ‘Minogue’ and I have seen others for sale on the continent.

Like all the onions here, they are worth the effort to track down and grow. And don’t stop there – once you scratch the surface of the onion family you’ll find there are many layers to discover!

After scrambling through some of the various branches of horticulture, Vicki realised that food production was where her heart is (or should that be stomach!). She spent six years growing traditional UK vegetable varieties for seed at Garden Organic’s Heritage Seed Library. In 2014 she began a new chapter at Hampton Court Palace, recreating a section of the original walled kitchen garden - so she can now grow historic favourites in an historic setting. View all posts by Vicki.

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